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src/ResourceLister.js

/*
 * BSD 3-Clause License
 *
 * Copyright (c) 2018, MapCreator
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 *  Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 *  Neither the name of the copyright holder nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

import { snake as snakeCase } from 'case';
import { EventEmitter } from 'events';
import Maps4News from './Maps4News';
import RequestParameters from './RequestParameters';
import ResourceBase from './resources/base/ResourceBase';
import { isParentOf } from './utils/reflection';

/**
 * Paginated resource lister
 *
 * @fires ResourceLister#update
 */
export default class ResourceLister extends EventEmitter {
  /**
   * ResourceLister constructor
   *
   * @param {Maps4News} api - Api instance
   * @param {string} route - Resource url route
   * @param {constructor<ResourceBase>} Resource - Resource constructor
   * @param {?RequestParameters} parameters - Request parameters
   * @param {number} [maxRows=50] - Initial max rows
   * @param {string} [key=id] - Key
   */
  constructor (api, route, Resource = ResourceBase, parameters = null, maxRows = 50, key = 'id') {
    super();

    if (!isParentOf(Maps4News, api)) {
      throw new TypeError('Expected api to be of type Maps4News');
    }

    this._api = api;
    this._Resource = Resource;
    this._route = route || (new this.Resource(api, {})).baseUrl;
    this._parameters = new RequestParameters(parameters || { perPage: RequestParameters.maxPerPage });
    this._key = snakeCase(key);
    this._waiting = false;

    this.autoUpdate = true;
    this.maxRows = maxRows;

    this._reset();
  }

  /**
   * Get if there are more resources to fetch. It indicates if the maxRows can be increased.
   * @returns {boolean} - if more rows are available
   */
  get hasMore () {
    return typeof this.availableRows === 'undefined' || this.availableRows > this.maxRows;
  }

  /**
   * Get if the instance is waiting for data
   * @returns {boolean} - waiting for data
   */
  get waiting () {
    return this._waiting;
  }

  /**
   * Get the request parameters
   * @returns {RequestParameters} - parameters
   */
  get parameters () {
    return this._parameters;
  }

  /**
   * Set the request parameters
   *
   * If you set {@link ResourceLister#autoUpdate} to true then {@link ResourceLister#update}
   * will automatically be called when the parameters are updated.
   * @throws {ResourceLister#autoUpdate}
   * @param {RequestParameters} object - parameters
   */
  set parameters (object) {
    this.parameters.apply(object);
  }

  /**
   * Resource constructor accessor, used for building the resource instance
   * @returns {constructor<ResourceBase>} - resource constructor
   */
  get Resource () {
    return this._Resource;
  }

  /**
   * Get the route (url)
   * @returns {string} - route
   */
  get route () {
    return this._route;
  }

  /**
   * Get the data
   * @returns {Array<ResourceLister.Resource>} - data
   */
  get data () {
    return this._data;
  }

  /**
   * Get the api instance
   * @returns {Maps4News} - api instance
   */
  get api () {
    return this._api;
  }

  /**
   * Get the row count
   *
   * @see {ResourceLister.data}
   * @returns {number} - row count
   */
  get rowCount () {
    return this.data.length;
  }

  /**
   * Get the maximum amount of rows allowed
   * @returns {number} - max rows
   */
  get maxRows () {
    return this._maxRows;
  }

  /**
   * Set the maximum amount of rows allowed
   * @param {number} value - max rows
   */
  set maxRows (value) {
    value = Number(value);

    if (Number.isNaN(value)) {
      throw new TypeError(`Expected maxRows to be numeric got ${typeof raw}`);
    }

    this._maxRows = value;

    if (this.autoUpdate) {
      // noinspection JSIgnoredPromiseFromCall
      this.update();
    }
  }

  /**
   * Get the number of rows the server has available
   * @returns {number} - number of rows
   */
  get availableRows () {
    return this._availableRows;
  }

  /**
   * Set if {@link ResourceLister#update} should be called when {@link ResourceLister#parameters} is updated
   *
   * @throws {ResourceLister#update}
   * @throws {ResourceLister#parameters}
   * @param {boolean} value - auto update
   */
  set autoUpdate (value) {
    value = Boolean(value);

    if (this.autoUpdate !== value) {
      this._autoUpdate = value;

      if (typeof this._boundUpdate === 'undefined') {
        this._boundUpdate = this.update.bind(this);
      }

      if (this.autoUpdate) {
        this.parameters.on('change', this._boundUpdate);
      } else {
        this.parameters.off('change', this._boundUpdate);
      }
    }
  }

  /**
   * Get if {@link ResourceLister#update} should be called when {@link ResourceLister#parameters} is updated
   *
   * @throws {ResourceLister#update}
   * @throws {ResourceLister#parameters}
   */
  get autoUpdate () {
    return this._autoUpdate;
  }

  /**
   * Reset the instance
   *
   * @private
   */
  _reset () {
    this._parameterToken = this.parameters.token();

    this._realData = [];
    this._data = [];
    this._keys = [];

    delete this._availableRows;
  }

  /**
   * Update the server data
   */
  async update () {
    if (this.waiting) {
      return;
    }

    this._waiting = true;

    try {
      if (this._parameterToken !== this.parameters.token()) {
        this._reset();
      }

      if (this._realData.length < this.maxRows) {
        try {
          await this._fetchMore();
        } catch (e) {
          this.autoUpdate = false;

          this.emit('error', e);

          throw e;
        }
      }

      if (this.data.length !== this.maxRows) {
        this._data = this._realData.slice(0, this.maxRows);
      }
    } finally {
      this._waiting = false;
    }

    /**
     * Update event.
     * Called when the ResourceLister has updated
     *
     * @event RequestLister#update
     */
    this.emit('update');
  }

  /**
   * Fetch more data from the server
   * @private
   */
  async _fetchMore () {
    const glue = this.route.includes('?') ? '&' : '?';
    const parameters = this.parameters.copy();

    parameters.offset += this.rowCount;

    const endPage = Math.ceil((this.maxRows - this.rowCount) / this.parameters.perPage);
    const promises = [];

    for (; parameters.page <= endPage; parameters.page++) {
      const url = this.route + glue + parameters.encode();
      const promise = this.api.axios.get(url);

      promises.push(promise);
    }

    const responses = await Promise.all(promises);

    for (const { data: { data }, headers } of responses) {
      data.forEach(row => this.push(row, false));

      this._availableRows = Number(headers['x-paginate-total']) + parameters.offset;
    }
  }

  /**
   * Returns the iterable
   * @returns {Iterator} - iterator
   */
  [Symbol.iterator] () {
    return this.data[Symbol.iterator]();
  }

  /**
   * Push a row to the data collection
   *
   * This will append the row or update an existing row based on the key. If
   * autoMaxRows is set to true and maxRows only needs to be increased by one
   * for the new resource to show up it will
   * @param {ResourceLister.Resource} row - resource
   * @param {boolean} autoMaxRows - Increase maxRows if needed
   */
  push (row, autoMaxRows = true) {
    if (!isParentOf(this.Resource, row)) {
      row = new this.Resource(this.api, row);
    }

    const index = this._keys.findIndex(i => i === row[this._key]);

    if (index >= 0) {
      this._realData[index] = row;

      if (typeof this._data[index] !== 'undefined') {
        this._data[index] = row;
      }
    } else {
      this._realData.push(row);

      this._keys.push(row[this._key]);

      if (autoMaxRows) {
        this.maxRows++;

        this._data.push(row);
      }
    }
  }

  /**
   * Same as `this.maxRows += this.parameters.perPage`
   * @param {number} [rows=parameters.perPage] - Amount to increment maxRows with
   */
  loadMore (rows = this.parameters.perPage) {
    this.maxRows += rows;
  }
}